Land Rover Repair: 96 Disco misfires, fast idle, ...... ECU ?, throttle position sensor, land rover discovery

Question
HI JOHN,
  I OWN A 1996 LAND ROVER DISCOVERY PETROL 4.0
67,000 MILES ON IT.  WHEN I START IT IN THE MORNING, THE IDLE IS FAST AND DOESN'T DROP DOWN UNTIL IT'S IN GEAR AND THEN THE IDLE IS RUFF LIKE
IT'S MISSING. SOMETIMES ON WARM DAYS IT FEELS LIKE THE TRANNY IS DRAGGING AND WHEN DRIVING AT HIGHER SPEEDS THE ENGINE LOSES POWER FOR A FEW SECONDS AND THEN RUNS OK FOR A WHILE AND DOES IT AGAIN. IT DID THIS STUNT FROM LOS ANGELES TO LAS VEGAS, THAT WAS BAD ! THE CHECK ENGINE LIGHT IS
READING 1316 FOR MONTHS.

   THE ENGINE WAS REBUILT AT 55,000 MILES.
AT 66,000 PLUGS WERE CHANGED (AND THEY WERE CLEAN)... WIRES WERE CHANGED ...COIL PACKS WERE CHANGED, STEPPER MOTOR WAS REPLACED AND ALL FOUR O2 SENSORS WERE REPLACED AND NEW CATALYLIC CONVERTERS . ONE ROVER TECH MENTIONED, IT MIGHT BE THE COMPUTER ECU ?... IS IT POSSIBLE ?
COULD THE COMPUTER BE TELLING THE ENGINE TO ACT
BADLY ?  I'M READY TO RUN THIS PIG OFF A CLIFF !   
                       DESPERATE  

Answer
Hi John,

tough call.  Looks like the usual suspects have been swapped out.  Throttle position Sensor (TPS) can do this type of behaviour as can the Mass Air Flow (MAF) sensor.  TPS ($200) is cheaper to swap than the MAF ($800+).

I had the same behaviour on my '95 and it turned out to be the TPS.  Problem was...the dealer did close to $5000 in repairs before finally finding the real culprit (TPS).

Best of luck,

JohnMc

NB:  I know of a few good cliffs in your area! Trouble is....you have to drive to get there. :)